Prior to his 2010 appearance as William Bell on "Fringe," the
"Star Trek" star, in no uncertain terms, said he was retiring from acting. He
would concentrate on his photography and just enjoy life.

But since then, he has done voiceover work on "Transformers:
Dark of the Moon" and "The Big Bang Theory." He appeared as a cartoon Bell in
another episode of "Fringe" and has reappeared in the flesh for the show's
two-part season finale (concluding tonight at 9 p.m. on FOX).

So what gives?

"I'm a sucker for a good role," Nimoy said with a chuckle.
"And J.J. Abrams, the executive producer of the show, is a friend of mine. He
calls. I take his call. The writers and producers - Joel Wyman, Jeff Pinkner -
and the cast, they're a wonderful bunch of people and I enjoy being there. When
they called and asked me if I would do it, it was pretty easy to convince me
that there was an interesting challenge in the character and a very wonderful
company to work with."

"Fringe" fans (myself, included) are thrilled to see Nimoy
back in the fold. The 81-year-old actor said he was excited about the prospect
of returning to the series.

"It's not just the role of William Bell. It's the show,"
Nimoy said. "I think 'Fringe' is a wildly imaginative show. The writers and the
creators of the show, the producers, are very bright and very theatrical. All
the characters are fleshed out wonderfully and the chemistry amongst the cast
is terrific. I wanted to be part of this project. I enjoy the project."

Nimoy's return to "Fringe" comes at an interesting point in
the show's history. Like his own television show, "Star Trek," "Fringe" is
adored by critics and sci-fi fans, but somewhat ratings challenged.

"If I could answer that question, I think the networks
would all be on me for explanations of what to do about their schedules," he
said. "I'm not an authority on ratings and how these things happen. You're
absolutely right in the comparison to 'Star Trek.' We did very poorly in the
ratings, but eventually the show started to become more and more popular, until
it became a news story where stations were carrying the show at various hours
and various time and sometimes in marathons on weekends and 6 p.m. every night
in syndication.

"The same thing could happen with 'Fringe.' I can tell you
that when 'Star Trek' was put on a Friday night, which is a date night, not a
good night for a show like this, it did very, very poorly. 'Fringe' has the
same kind of audience: A very intense audience, a small audience, but very
intense and very committed. I think it's commendable that the people at FOX
decided to honor that commitment.

"Now I understand that the show does particularly well in
DVR recordings, and I don't know how that works or how they measure that. What
that means is that people who are out on Friday nights record the show and
watch it some other time. That's a sign of the commitment to the show."

Nimoy has left the door open to return for "Fringe's" fifth
and final season.

"I'm sure that we will be having conversations about that
before too long," he said. "I haven't heard anything new about William Bell or
the show, except that it has been picked up for 13 episodes, which I think is
wonderful."

"I'm excited about the show," Nimoy said. "I'm proud to be
connected with 'Fringe.' I think it's an intelligent and imaginative and
theatrical show. I told the company when I finished shooting on this particular
episode a few weeks ago, I said, 'You are superior company. I have never worked
with a better company in my entire 60-year career.' I thanked them all for
being who they are and doing what they are, and told them how proud I was to be
a part of it.

"I'm looking forward to (Friday) night myself. I have not
seen the show put together. I think it's going to be exciting for everybody."

"Fringe" airs Friday
at 9 p.m. on FOX. Follow the show on Twitter: @FRINGEonFOX.